Improvement of tribological, mechanical and chemical properties of Mg alloy (AZ91D) by electrophoretic deposition of alumina/GO coating

Although Mg alloys are excellent structural materials but their weak tribological and corrosion properties limit their widespread applications. In the present study we aimed to enhance the tribological, surface mechanical and corrosion properties of AZ91D Mg alloy by electrophoretic deposition of alumina/GO coatings (with 0.0, 0.5, 1.0, and 2.0 wt% of GO). The phase composition and microstructural features of the coatings were studied by X-ray diffraction and scanning electron microscopy techniques. Hardness, drop contact angle, and electrochemical impedance tests were conducted to investigate the various properties of the coatings. Our results show that electrophoretic deposition technique is capable of preparation of coatings with very low number of cracks, particularly when higher content of GO (2 wt%) is used. Although coating of only alumina already improved the alloy properties, but incremental addition of GO demonstrated significant improvement in hardness, scratch and corrosion resistances of the coatings. According to our results, the improvement in mechanical properties is mainly due to the effect of GO nanoplatelets in bridging between alumina nanoparticles. On the other hand, GO considerably boosts the corrosion resistance due to its effect in removing the cracks and open spaces from the microstructure. Overall, alumina/GO nanocomposite coatings prepared by electrophoretic deposition demonstrates comparable-level properties with those prepared in the previous researches by thermal spraying methods.